Marine motors and transmissions are typically controlled by throttles and clutches that are adjusted or moved by a pilot or captain during operation of a boat. Each throttle generally includes a control arm that is connected to a throttle assembly which, in turn, is connected via a cable to a marine engine. Similarly, each clutch typically includes a control arm that is connected to a clutch assembly which, in turn, is connected via a cable to a marine transmission. These control arms generally include a knob at one end which can be grasped by the pilot or captain in order to vary engine speed or direction.
Each control arm typically includes knurls (or ridges) for coupling the control arm to either a throttle or clutch assembly. More particularly, each control arm typically includes a round knurl socket with ridges that mate with corresponding grooves a throttle or clutch assembly when the control arm and the throttle or clutch assembly are interconnected. The knurls or ridges in the knurl socket are usually quite small, and typically have a height which is on the order of a millimeter.
In order for the knurl socket in the control arm to function properly, it is critical that the socket have a roundness that matches the round contour of the throttle or clutch assembly to which the control arm will be connected. In addition, it is critical that the knurls or ridges in the socket be present in a proper dimension.
When certain metals are cast into parts (and, in particular, when stainless steel is cast into parts), the shrinkage of the part within a mold will vary unevenly if the weight of the part is not evenly distributed throughout the mold. Since a knurl socket is typically of a greater mass than the remaining portion of its associated control arm, it is difficult to cast both the knurl socket and the control arm in a single piece without uneven shrinkage occurring during the casting process. Such uneven shrinkage will typically result in a loss of roundness in the knurl socket of the control arm.
In addition, the dimension of each knurl in the socket (typically on the order of a single millimeter in height) is substantially smaller than the handle portion of the control arm which will often be about eight inches in dimension. Given the relatively large size of the handle portion in relation to the knurls, it is difficult to cast both handle portion and the knurls in a single casting. This difficulty arises from the fact that the fluidness of metal decreases during the casting process as the metal begins to cool. Since the knurl socket is located at one end of the control arm, it is likely that some or all of the individual knurls in the socket might not cast if the knurl socket and the control arm are formed in a single casting.
Marine control arms and knobs are typically positioned near the steering wheel of a craft, and are often positioned at locations which expose the control arms and knobs to the outside elements such as ultraviolet radiation from the sun, wind and rain. In order for a pilot or captain to clearly distinguish between the throttle and clutch during operation of a boat, the knob used for controlling the marine throttle is generally labeled with the color red, and the knob used for controlling the marine clutch is generally labeled with the color black. However, as a result of exposure to the outside elements, these control knobs often lose some or all of their initial coloration. Control knobs with deteriorated coloring are unsightly. More importantly, however, when the control knobs have deteriorated coloring, it is more difficult for a pilot or captain to distinguish between the throttle and clutch during operation of a boat.
It is therefore an object of the present invention to provide a marine control arm with a round knurl socket in which all of the knurls in the socket have been properly cast.
It is a further object of the present invention to provide control knobs which are easily distinguishable and which do not lose coloration as a result of exposure to the outside elements.
It is a still further object of the present invention to provide control knobs which are distinguishable not only by virtue of their color, but also as a result of their surface feel and texture.
It is a still further object of the present invention to provide improved control knobs which can be used in connection with existing control arms as replacements for deteriorated knobs which may be affixed to such control arms.
These and other objects and advantages of the invention will become more fully apparent from the description and claims which follow or may be learned by the practice of the invention.